Note: Descriptions are shown in the official language in which they were submitted.
CA 02843757 2014-02-25
Attorney Docket No. 20120762CA01 (0010.0392)
STABILIZING POLYMERS TO CONTROL PASSIVE LEAKING OF FUNCTIONAL
MATERIALS FROM DELIVERY MEMBERS
BACKGROUND
[0001] Embodiments herein relate generally to image forming apparatuses (e.g.,
electrophotographic apparatuses and printers) and components for use therein.
Some
embodiments are drawn to improved delivery members for delivery (directly or
indirectly) of a functional material to the surface of an imaging member
(e.g.,
photoreceptor) in an image forming apparatus to reduce printing defects and
extend the
useful lifespan of the imaging member.
[0002] In electrophotographic printing, the charge retentive surface/imaging
member,
also known as a photoreceptor, is electrostatically charged by a charging unit
(e.g., a
bias charge member), and then exposed to a light pattern of an original image
to
selectively discharge the surface in accordance therewith. The resulting
pattern of
charged and discharged areas on the photoreceptor form an electrostatic charge
pattern, known as a latent image, conforming to the original image. The latent
image is
developed by contacting it with toner or developer.
[0003] Long life photoreceptors can result in significant run-cost reductions.
Improvement of long life photoreceptors has included the development of low
wear
protective overcoat layers. These protective overcoat layers can help
dramatically
reduce surface wear of imaging members. However, these layers can also
introduce a
host of unwanted issues caused by the poor interaction between a cleaning
blade and
the overcoat layer and increased lateral charge migration (LCM). The overcoats
can be
associated with extremely high initial torque and can result in print defects,
poor
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cleaning, cleaning blade damage/failure and cleaning blade flip, and, in some
cases,
high initial torque can prevent the imaging member from turning and can cause
a
motor fault. High torque can induce mechanical stress and vibration in the
cleaning
blade, which can, in turn, result in deformation and acoustic squeaking of the
blade.
This can damage the blade surface enough to permit permanent toner
contamination
of the imaging member. The contamination is often characterized by lines of
toner
around the circumference of the imaging member that correlate with the damaged
areas of the cleaning blade.
[0004] The performance of overcoated imaging members can be improved by
applying a thin film of a functional material/lubricant (e.g., paraffin oil)
using an
extrinsic delivery system (such as a delivery member) to address both the LCM
and
friction/torque problems. The thin film of functional material can act to
lubricate a
cleaning blade. Examples of methods and apparatuses related to application of
functional materials to address these problems are described in copending U.S.
Patent Application Nos. 13/020,738 (U.S. Publication No. 20120201585);
13/192,215
(U.S. Publication No. 20130028636); 13/192,252 (U.S. Publication No.
20130028637); 13/279,981; and 13/437,472.
[0005] An issue related to certain delivery members having an outer
polydimethylsiloxane (PDMS) matrix that deliver a paraffin oil to an imaging
member
is that the paraffin oil can passively diffuse from the PDMS matrix (even
without
being in contact with another object, such as a bias charge roll (BCR)). This
passive
diffusion of the paraffin oil out of the delivery member can cause the
paraffin oil to
pool against a BCR or imaging member when an image forming apparatus sits idle
(e.g., as when turned off overnight). The passive leaking of paraffin oil from
a
delivery member is detrimental to an image forming apparatus (e.g., printer),
because over-delivery of
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paraffin oil increases contamination and causes print defects (e.g., streaking
or lack of
toner development); and consumes/wastes the supply of paraffin oil.
[0006] It would be desirable to maximize the amount of functional material
(such as
paraffin oil) stored in a delivery member in order to maximize the delivery
member's
lifetime. However, passive diffusion of functional material is greater at
higher loadings
of functional material relative to the elastomer matrix in delivery members,
such as in
delivery members having high loadings of paraffin oil dispersed in a PDMS
matrix.
Thus, it would be desirable to reduce or minimize passive leaking of
functional material
from delivery members.
SUMMARY
[0007] Certain embodiments are drawn to delivery members for use in image
forming
apparatuses. The delivery members include a support member and a first layer
disposed on the support member. The first layer has a cross-linked elastomeric
matrix,
a stabilizing polymer comprising a polysiloxane backbone, and a functional
material.
[0008] Some embodiments are drawn to a coating mixture for a delivery member
containing an elastomer capable of being cross-linked, a stabilizing polymer
comprising
a polysiloxane backbone, and a functional material.
[0009] Certain embodiments are directed to image forming apparatuses that
include an
imaging member having a charge retentive surface, a charging unit for applying
an
electrostatic charge on the imaging member; and a delivery member disposed in
contact with a surface of the imaging member or a surface of the charging
unit. The
delivery member has a support member, and a first layer, including a cross-
linked
elastomeric matrix, a stabilizing polymer comprising a polysiloxane backbone,
and a
functional material, that is disposed on the support member.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates two configurations of a delivery member (e.g., a
delivery roller)
in an image forming apparatus. The delivery member can be configured to apply
a thin
film of a functional material: a) directly to the surface of an imaging
member; or b) to a
charging unit which then transfers the material to the surface of the imaging
member.
FIG. 2 depicts a print test performed using an image forming apparatus with a
delivery
member comprising a polydimethylsiloxane (PDMS) matrix/paraffin oil delivery
roller
disposed for application of paraffin oil on two-thirds of the length of a
photoreceptor in
the image forming apparatus after 32,500 prints.
[0011] FIG. 3 is a scanning electron microscopy (SEM) image showing paraffin
oil-filled
pores dispersed in a solid PDMS matrix.
[0012] FIG. 4 shows photos of samples of a) PDMS:paraffin oil 2:1, b)
PDMS:paraffin
oil:MHOMS (methylhydrosiloxane-octylmethyl siloxane copolymer) 2:1:0.5, and c)
PDMS:paraffin oil:pTDMS (polytetradecylmethylsiloxane) 2:1:0.5 in polystyrene
petri
dishes about 24 days after they were prepared. (Ratios were by weight.)
[0013] FIG. 5 shows photos of delivery rollers prepared with formulations by
weight: a)
PDMS:paraffin oil 2:1, b) PDMS:paraffin oil:MHOMS 2:1:0.5, and c)
PDMS:paraffin
oil:pTDMS 2:1:0.25 in contact with a bias charge roll (BCR) for 24 hours.
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[0014] FIG. 6 shows photos of delivery rollers prepared with formulations by
weight: a)
PDMS:paraffin oil 2:1, b) PDMS:paraffin oil:pTDMS 2:1:0.5, and c)
PDMS:paraffin
oil:pTDMS 2:1:0.25 in contact with a bias charge roll (BCR) for about 5 days.
[0015] FIG. 7 depicts print tests performed with an image forming apparatus
having a
delivery roller comprising by weight a) PDMS:paraffin oil 2:1, and b)
PDMS:paraffin
oil:pTDMS 2:1:0.5 after aging about 24 hours and 0 prints.
[0016] FIG. 8 depicts print tests performed with an image forming apparatus
having a
delivery roller comprising by weight a) PDMS:paraffin oil 2:1, and b)
PDMS:paraffin
oil:pTDMS 2:1:0.5 after aging about 5 days and 0 prints.
[0017] FIG. 9 shows photos of delivery rollers comprising by weight a)
PDMS:paraffin
oil 2:1; and b) PDMS:paraffin oil:pTDMS 2:1:0.5 after aging about 5 days and
100
prints.
[0018] FIG. 10 depicts a print test performed with an image forming apparatus
having a
delivery roller comprising PDMS:paraffin oil 2:1 by weight after aging about 5
days and
100 prints.
[0019] It should be noted that some details of the figures have been
simplified and are
drawn to facilitate understanding of the embodiments rather than to maintain
strict
structural accuracy, detail, and scale.
DETAILED DESCRIPTION
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[0020] A delivery member of embodiments can be integrated into an image
forming
apparatus in various configurations and positions. As an imaging member in an
image
forming apparatus moves, the delivery member can deliver a functional material
directly
to the surface of the imaging member or to the surface of a charging unit
(which in turn
delivers the functional material to the imaging member). Certain embodiments
can be
better understood with reference to the Drawings.
[0021] FIG. 1A illustrates one configuration of elements in an image forming
apparatus.
A delivery member 10 (e.g., delivery roll), an imaging member 20 (e.g.,
photoreceptor)
and a charging unit 30 (e.g., bias charge roll (BCR)) are shown. The delivery
member
contacts the imaging member 20 (e.g., photoreceptor) to deliver a layer 40
(e.g., an
ultrathin layer of from about 1 nm to 200 nm, from about 5 nm to about 50 nm,
or from
about 8 nm to about 20 nm.) of a functional material (e.g., paraffin oil,
among others
known in the art) onto the surface of the imaging member 20. The imaging
member 20
can be charged by the charging unit 30 (e.g., BCR) to initiate an
electrophotographic
reproduction process. The imaging member can be exposed to alter its surface
charge
thereby creating an electrostatic latent image on the imaging member. This
latent
image can subsequently be developed into a visible image by a toner developer.
Thereafter, the developed image can be transferred from the imaging member to
a copy
sheet or some other image support substrate to which the image may be
permanently
affixed. The imaging member surface can be cleaned with a cleaner (e.g., a
cleaning
blade) to remove any residual developer or other contaminant in preparation
for
successive imaging cycles.
[0022] In an alternative configuration shown in FIG. lb, the delivery member
10 contacts
the charging unit 30 (e.g., BCR) to deliver a thin layer 50 of the functional
material onto
the surface of the charging unit. The charging unit 30, in turn, transfers the
functional
material onto the surface of the imaging member 20 (e.g., photoreceptor) as a
thin layer
40 (e.g., molecular hydrophobic layer).
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[0023] A delivery member according to embodiments can be used in an imaging
forming
apparatus or a subsystem of such an apparatus. In embodiments, the delivery
member
can be a component of a customer replaceable unit (CRU) of a xerographic
printing
system and deliver a functional material to the outer layer, for example, a
protective
overcoat layer, of an imaging member/photoreceptor. The imaging member can
have a
composition/structure known in the art.
[0024] An imaging member/photoreceptor can comprise at least a substrate
layer, an
imaging layer disposed on the substrate and an optional overcoat layer
disposed on the
imaging layer. The imaging layer can comprise a charge generation layer
disposed on
the substrate and a charge transport layer disposed on the charge generation
layer. In
other embodiments, an undercoat layer can be included and can be located
between
the substrate and the imaging layer, although additional layers can be present
and
located between these layers. The imaging member can also optionally include
an anti-
curl back coating layer. The imaging member can comprise a support substrate,
an
electrically conductive ground plane, an undercoat layer, a charge generation
layer and
a charge transport layer, in certain embodiments. An optional protective
overcoat layer
can be disposed on the charge transport layer. The charge generation layer and
the
charge transport layer can form an imaging layer as two separate layers. In an
alternative configuration, the functional components of these two layers can
be
combined in a single layer.
[0025] In some embodiments, the imaging member can have a drum, cylinder,
plate,
belt or drelt configuration, among others known in the art. In a belt
configuration, the
imaging member can comprise an anti-curl back coating, a supporting substrate,
an
electrically conductive ground plane, an undercoat layer, an adhesive layer, a
charge
generation layer, and a charge transport layer, in some embodiments. An
overcoat
layer and ground strip can be included in an imaging member, in certain
embodiments.
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[0026] An overcoat layer can be disposed over the charge transport layer to
provide
imaging member surface protection as well as improve resistance to abrasion.
The
overcoat layer can be any known in the art for use with imaging members. The
overcoat layer can have a thickness ranging from about 0.1 micrometers to
about 25
micrometers or from about 1 micrometer to about 10 micrometers, or in a
specific
embodiment, about 3 micrometers to about 10 micrometers. The overcoat layer
can
comprise a charge transport component and an optional organic polymer or
inorganic
polymer, in some embodiments. Certain overcoat layers can comprise
thermoplastic
organic polymers or cross-linked polymers, such as thermosetting resins, UV or
e-beam
cured resins, and the like. In some embodiments, the overcoat layer can
include a
particulate additive, such as metal oxides including aluminum oxide and
silica, or low
surface energy polytetrafluoroethylene (PTFE), or a combination thereof.
[0027] Certain embodiments can result in significant run-cost reductions due
to their
increasing the life of imaging members. As discussed above, it is known in the
art that
robust overcoats can extend the life of imaging members, but incorporation of
such
overcoats into commercially successful devices has been hindered due to
increased
lateral charge migration (LCM) and friction between the cleaning blade and the
surface
of such overcoats. The performance of overcoated imaging members can be
improved
by applying a thin film (from about 1 nm to 200 nm, from about 5 nm to about
50 nm, or
from about 8 nm to about 20 nm) of a functional material/lubricant (e.g.,
paraffin oil)
using an extrinsic delivery system to address both the LCM and friction/torque
problems. The thin film can act to lubricate a cleaning blade.
[0028] A delivery member can be used to apply a layer of paraffin oil and/or
other
functional material to the surface of a photoreceptor/imaging member either
directly
(FIG. la) or via a charging unit (e.g., bias charge roll (BCR)) (FIG. lb). The
paraffin oil
or other functional material can act both as a lubricant that reduces torque,
and as a
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sacrificial layer that protects the overcoat of a photoreceptor/imaging member
from
damage caused by charging (by, for example, a BCR). BCR charging generates
hydrophilic species in an organic film/overcoat, which can result in lateral
charge
migration (e.g., A-Zone deletion). FIG. 2 shows a print where a delivery
roller with an
outer layer of polydimethylsiloxane (PDMS) matrix mixed with paraffin oil was
in contact
with two-thirds of the length of a photoreceptor. The side that was in contact
with the
delivery roller shows no deletion, whereas the side without the roller (e.g.,
without
applied paraffin oil) shows deletion and streaking.
[0029] Delivery members according to present embodiments can contain
sufficient
quantities of the functional material to continuously supply a thin or ultra-
thin layer of
less than about 10 nm of the functional material to the surface of the
charging
unit/imaging member in an image forming apparatus. The functional material can
diffuse from the first layer to the surface of the delivery member, where it
is transferred,
directly or indirectly (via the charging unit), to an imaging member in an
image forming
apparatus.
[0030] A delivery member can be fabricated having a cross-linked elastomeric
matrix in
which a functional material is dispersed. The cross-linked elastomeric and the
functional
material can be incompatible materials, which can contribute to a high rate of
diffusion
of the functional material from the cross-linked elastomeric matrix. For
example, PDMS
(elastomeric matrix) and paraffin oil (functional material) are incompatible
materials (i.e.,
silicone oil and paraffin oil are immiscible materials), and the
incompatibility can cause
the paraffin oil to passively diffuse out of a PDMS matrix even without the
delivery
member being in contact with another component, such as a BCR.
[0031] Passive diffusion of functional material (e.g., paraffin oil) out of a
delivery
member can cause functional material (i.e., paraffin oil) to pool against a
charging unit
or an imaging member when an image forming apparatus sits idle. Excessive
amounts
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of functional material can cause image defects and can contribute to toner
contamination. The passive diffusion can be greater at higher functional
material:cross-
linked elastomeric matrix (e.g., paraffin oil:PDMS matrix) ratios by weight,
but passive
diffusion can be minimized by lowering the amount of functional material
stored in the
cross-linked elastomeric matrix. To reduce contamination, while maintaining
the
necessary reservoir of functional material it would be desirable to better
control passive
leaking of functional material from a delivery member. Certain embodiments can
control
passive leaking by employing a first layer in a delivery member comprising a
stabilizing
polymer that can stabilize the functional material dispersed within the cross-
linked
elastomeric matrix that is a component of a delivery member.
[0032] Certain embodiments are drawn to delivery members comprising a support
member and a first layer comprising a cross-linked elastomeric matrix, a
stabilizing
polymer comprising a polysiloxane backbone, and a functional material. The
first layer
is disposed on the support member. The functional material can diffuse to the
surface of
the delivery member in embodiments. In embodiments, the functional material
can be
dispersed in the cross-linked elastomeric matrix. The amount of the functional
material
delivered onto the surface of an imaging member or a charging unit is
controlled (at
least in part) by the diffusion rate of the functional material in the first
layer.
[0033] In some embodiments the support member of the delivery member can
comprise
metal, plastic, ceramic, or a mixture of two or more thereof. In certain
embodiments the
support member of the delivery member can be a stainless steel rod. The
diameter of
the support member can be varied depending on the application needs. In some
embodiments, the support member can have a diameter of between about 3 mm and
about 10 mm.
[0034] The delivery member comprises a first layer comprising a cross-linked
elastomeric matrix disposed around the support member. The cross-linked
elastomeric
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matrix can comprise at least one cross-linked polymer. In certain embodiments,
the
polymer that is cross-linked can be selected from the group consisting of
silicones,
fluorosilicones, polyurethanes, polyesters, polyfluorosiloxanes,
fluoroelastomers,
synthetic rubbers, natural rubbers, and mixtures of two or more thereof. The
cross-
linked elastomeric matrix can comprise cross-linked polydimethylsiloxane
(PDMS), in
some embodiments.
[0035] As discussed above, in embodiments the first layer comprises a
functional
material dispersed within a cross-linked elastomeric matrix. The functional
material can
provide improved maintenance of desired photoreceptor function. It can provide
lubrication and surface protection to a photoreceptor/imaging member. The thin
layer of
functional material on the imaging member can be provided on a nano-scale or
molecular-level, and can act as a barrier against moisture and surface
contaminants
and improve xerographic performance in high humidity conditions, such as for
example
A-zone environments (e.g., 28 C, 85% relative humidity).
[0036] Not to be bound by theory, A-zone deletion can be caused by a number of
occurrences, including, high energy charging which results in the formation of
hydrophilic chemical species (e.g., -OH, -COOH) on the imaging member surface,
water
being physically absorbed on the imaging member surface in a humid
environment, and
an increase in the surface conductivity of the imaging member due to the
absorbed
water layer and toner contaminants. In embodiments, there can be controlled
delivery
of a thin layer of a functional material, such as a hydrophobic material, to
the surface of
an imaging member (e.g., low-wear overcoated photoreceptor) to reduce or
prevent A-
zone deletion.
[0037] Integration of a functional material into the composition of the
delivery member
can eliminate the need for a separate supply of materials within the system or
the need
to constantly reapply the material to the delivery member in embodiments.
Thus, the
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delivery member can act as both a reservoir and distributor for the functional
material.
The delivery members can contain sufficient quantities of a functional
material to
continuously supply a thin or ultra-thin layer of functional material to the
surface of a
charging unit/imaging member to extend the life of the imaging member.
[0038] In embodiments, the functional material can be an organic or inorganic
compound, a monomer or a polymer, or a mixture thereof. The functional
material can
comprise a lubricant material, a hydrophobic material, an oleophobic material,
an
amphiphilic material, or a mixture of two or more thereof. The functional
material can be
in the form of a liquid, a wax, a gel, or a mixture of two or more thereof. In
certain
embodiments, the functional material can comprise a material selected from the
group
consisting of alkanes, fluoroalkanes, silicone oils, mineral oil, synthetic
oils, natural oils,
and mixtures of two or more thereof. The functional material can include a
hydrophobic
compound or hydrophobic polymer, in some embodiments. In certain embodiments,
the
functional material can comprise a paraffin oil. In some embodiments, the
functional
material can comprise a paraffin oil having a specific viscosity between about
50 mPa.s
and about 230 mPa.s, between about 80 mPa.s and about 180 mPa.s, or between
about 100 mPa.s and about 145 mPa-s.
[0039] In some embodiments, the stabilizing polymer can comprise a
polysiloxane
backbone and a repeating unit having formula l
CH3
I
--ESi-0-17
I
[0040] R1 I
[0041] wherein R1 of each repeating unit is selected from the group consisting
of
substituted and unsubstituted alkyl groups, branched alkyl groups, alkylaryl
groups, and
arylalkyl groups; R1 of each repeating unit comprises from about 3 carbon
atoms to
about 30 carbon atoms, about 14 carbon atoms to about 18 carbon atoms, or
about 16
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carbon atoms to about 18 carbon atoms; R1 is the same or different for all
repeating
units having formula I in the stabilizing polymer; and x is between about 5
and about
5000 repeating units, about 5 and about 1000 repeating units; or about 5 and
about 500
repeating units. In certain embodiments, R1 is an alkyl group. R1 can be a C14
to C18
group; a C14 to C16 group; or a C16 to C18 group, in some embodiments.
[0042] In certain embodiments, the stabilizing polymer can comprise a
polysiloxane
having formula II
CH3 CH3 R2 CH3
l I Il
H3C-Si-O-F-SI- a 0 1 1 Si-0-t-Si-CH3
I I 1 b 1
[0043] CH3 R1 CH3 CH3 11
[0044] wherein Ri is selected from the group consisting of substituted and
unsubstituted
alkyl groups, branched alkyl groups, alkylaryl groups, and arylalkyl groups;
R1
comprises from about 3 carbon atoms to about 30 carbon atoms, about 14 carbon
atoms to about 18 carbon atoms, or about 16 carbon atoms to about 18 carbon
atoms;
and R1 is the same or different for all repeating units containing R1; wherein
R2 is a
hydrogen or a methyl; and wherein a is from about 0.1 to about 0.95, about 0.3
to about
0.9, or about 0.5 to about 0.8, b is from about 0.05 to about 0.9, about 0.1
to about 0.7,
or about 0.2 to about 0.5 and a+b = 1 in the mole ratio a:b of repeating units
within the
polysiloxane having formula II. In certain embodiments, R1 is an alkyl group.
R1 can be
a C14 to C18 group; a C14 to C16 group; or a C16 to C18 group, in some
embodiments.
[0045] The stabilizing polymer can have a molecular weight (Mw) of between
about 100
and about 500,000; between about 100 and about 100,000; or between about 500
and
about 50,000. In some embodiments, the stabilizing polymer can be selected
from the
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group consisting of methylhydrosiloxane-octylmethyl siloxane (MHOMS)
copolymer,
polytetradecylmethylsiloxane (pTDMS), and mixtures thereof. In certain
embodiments,
the stabilizing polymer can be a poly(dimethylsiloxane-co-alkylmethylsiloxane)
wherein
the alkyl group can be a C14 to C18 group or a C16 to C18 group.
[0046] Stabilizing polymers, such as methylhydrosiloxane-octylmethyl siloxane
(MHOMS) copolymer and polytetradecylmethylsiloxane (pTDMS), have both siloxane
and alkane type structures. In embodiments, such polymers with both types of
structures can be used as stabilizing polymers to stabilize a functional
material (e.g.,
paraffin oil) in a cross-linked elastomeric matrix (e.g., PDMS matrix) of a
delivery
member, which can permit a higher loading of functional material within the
delivery
member, while reducing or preventing passive leaking.
[0047] A delivery member of some embodiments can have a cross-linked
elastomeric
matrix comprising cross-linked polydimethylsiloxane (PDMS), a functional
material
comprising a paraffin oil, and a stabilizing polymer comprising a repeating
unit having
formula I or formula II, as described above.
[0048] In certain embodiments, the first layer comprises between about 1
wt%
and about 80 wt%; about 5 wt% and about 50 wt%; or about 10 wt% and about
20 wt% of the stabilizing polymer relative to the total weight of the first
layer. The
first layer can comprise between about 20 wt% and about 80 wt%; about 30 wt%
and about 70 wt%; or about 50 wt% and about 60 wt% of the cross-linked
elastomeric matrix relative to the total weight of the first layer. In some
embodiments, the first layer can have a thickness of between about 20 pm and
about 100 mm; about 100 pm and about 30 mm; or between about 0.5 mm and
about 10 mm. In some embodiments, the first layer comprises pores having a
diameter of between about 10 nm and about 50 pm; about 20 nm and about 10
pm; or about 50 nm and about 5 pm. In embodiments, the weight ratio of
functional material to cross-linked elastomeric matrix can be between about
1:10
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and about 1:1; about 1:8 and about 11:20; or about 9:20 and about 11:20, or
expressed differently between about 10% (1:10) and about 50% (1:1); about 12%
and about 45% or about 45% and about 55%
[0049] The delivery member can be in the form of a delivery roller, a film, a
belt, a web,
or a blade applicator, in some embodiments. In certain embodiments, the
delivery
member can be a delivery roller. In some embodiments, the first layer can have
a
patterned outside surface or a smooth surface. The delivery member can have a
surface pattern comprising indentations or protrusions that have a three-
dimensional
shape. The surface pattern can comprise protrusions having a sphere shape, a
hemisphere shape, a rod shape, a polygon shape, or two or more of such shapes.
[0050] In certain embodiments the delivery member can further comprise a
second layer
disposed over the first layer, wherein the functional material can diffuse
therethrough.
The second layer can have a thickness of between about 0.1 pm and about 1 mm;
about 0.2 pm and about 0.9 mm; or about 0.3 pm and about 0.07 mm. The second
layer can comprise a material selected from the group consisting of
polysiloxanes,
polyurethanes, polyesters, polyfluorosiloxanes, polyolefins, fluoroelastomers,
synthetic
rubbers, natural rubbers, and mixtures of two or more thereof.
[0051] Some embodiments are drawn to methods of producing a delivery member
for
use in an image forming apparatus, the method comprising: applying to the
outer
surface of a support member a coating mixture (e.g., comprising an elastomer
capable
of being cross-linked, a stabilizing polymer comprising a polysiloxane
backbone, and a
functional material), and curing the coating mixture thereby forming a first
layer. In
certain embodiments, a functional material and a stabilizing polymer can be
mixed with
an elastomer capable of being cross-linked; cast around a support member (in a
mold,
for example); and cured to form a first layer over the support member, such
that the
stabilizing polymer and/or the functional material is dispersed in the
resulting cross-
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linked elastomeric matrix. After curing, the first layer of the coated support
member can
be further impregnated by immersion in a functional material (e.g., paraffin
oil) in
preparing a delivery member, in certain embodiments.
[0052] Delivery members can be fabricated by (a) mixing an elastomer capable
of being
cross-linked (such as, polydimethylsiloxane (PDMS)) with a functional material
(such as,
paraffin oil) and a stabilizing polymer (b) injecting the mixture into a mold
(containing a
support member), and (c) curing the elastomer to produce a cross-linked
elastomeric
matrix (such as a PDMS matrix). The functional material (i.e., paraffin oil)
can thereby
be dispersed in the matrix (FIG. 3 showing paraffin oil dispersed in a PDMS
matrix).
[0053] Certain embodiments are drawn to coating mixtures for a delivery member
comprising an elastomer capable of being cross-linked, a stabilizing polymer
comprising
a polysiloxane backbone, and a functional material. The elastomer capable of
being
cross-linked can be selected from the group consisting of silicones,
fluorosilicones,
polyurethanes, polyesters, polyfluorosiloxanes, fluoroelastomers, synthetic
rubbers,
natural rubbers, and mixtures of two or more thereof. In some embodiments, the
elastomer capable of being cross-linked can be polydimethylsiloxane. In
certain coating
mixtures, the stabilizing polymer comprising a polysiloxane backbone can be as
described above. In some coating mixtures, the stabilizing polymer can be
selected
from the group consisting of methylhydrosiloxane-octylmethyl siloxane (MHOMS)
copolymer, polytetradecylmethylsiloxane (pTDMS), and mixtures thereof.
The
functional material in the coating mixtures can be as described above. Such
coating
mixtures can be suitable for use in methods of producing a delivery member,
described
above.
[0054] In embodiments, the addition of stabilizing polymers that have both
siloxane
characteristics and alkane characteristics into a coating mixture for a
delivery member
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can help to stabilize the functional material (e.g., paraffin oil) in a cross-
linked
elastomeric matrix (e.g., PDMS matrix), thereby stopping or reducing passive
leaking.
[0055] Some embodiments are drawn to image forming apparatuses comprising: an
imaging member having a charge retentive surface, a charging unit for applying
an
electrostatic charge on the imaging member; and a delivery member disposed in
contact with a surface of the imaging member (e.g., surface of overcoat of a
photoreceptor) or a surface of the charging unit. The delivery member
comprises a
support member, and a first layer comprising a cross-linked elastomeric
matrix, a
stabilizing polymer comprising a polysiloxane backbone, and a functional
material,
wherein the first layer is disposed on the support member. An image formed
using
image forming apparatuses of embodiments can have little or no background
darkening
or streaking visible to the naked eye. In some embodiments, A-zone lateral
charge
migration (LCM) is reduced or prevented when forming an image with the image
forming
apparatus. In some embodiments, when a layer of functional material (such as a
layer
of paraffin oil) has been applied to an imaging member in an image forming
apparatus,
the resulting OD (measured optical density) can be between about 0.05 and
0.065 for
the background of an image formed by the apparatus, and in an image forming
apparatus having the same imaging member, but without a layer of the
functional
material, the OD can be about 0.046 or less.
[0056] The image forming apparatus of certain embodiments can have a
functional
material present on the surface of the imaging member in an amount of between
about
0.5 nanograms/cm2 and about 500 nanograms/cm2. In certain embodiments, the
image
forming apparatus can comprise a delivery member having a first layer
comprising
between about 1 wt% and about 80 wt% of the stabilizing polymer relative to
the total
weight of the first layer. In some embodiments, the image forming apparatus
can
comprise a delivery member having a weight ratio of functional material to
cross-linked
elastomeric matrix that is between about 1:10 and 3:5. In some embodiments, an
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image forming apparatus can comprise a charging unit comprising a biased
charging
roller (BCR) in direct contact with an imaging member, and a delivery member
can be
disposed in direct contact with a surface of the BCR, such that the delivery
member
applies the functional material onto the surface of the BCR, which in turn
delivers the
functional material onto the surface of the imaging member.
[0057] In some embodiments the image forming apparatus can comprise a delivery
member having a cross-linked elastomeric matrix comprising cross-linked
polydimethylsiloxane (PDMS), a functional material comprising a paraffin oil,
and a
stabilizing polymer comprising a repeating unit having formula I or formula
II, as
described above.
[0058] As discussed above, it is known in the art that robust overcoats can
increase
lateral charge migration (LCM), among other potential problems. The
performance of
overcoated imaging members can be improved by applying a thin film of a
functional
material/lubricant using a delivery member to address the LCM issue. As
detailed
above, A-zone deletion may be caused by high energy charging resulting in the
formation of hydrophilic chemical species (e.g., -OH, -COOH) on the imaging
member
surface, water being physically absorbed on the imaging member surface in an
humid/A-zone environment (e.g., 28 C, 85% relative humidity), and an increase
in the
surface conductivity of the imaging member due to the absorbed water layer and
toner
contaminants. A thin layer of functional material on the imaging member can be
provided on a nano-scale or molecular-level and act as a barrier against
moisture and
surface contaminants and improve xerographic performance in high humidity
conditions,
such as for example A-zone environments. In embodiments, there can be
controlled
delivery of a thin layer of a functional material, such as a hydrophobic
material, to the
surface of an imaging member (e.g., low-wear overcoated photoreceptor) in an
image
forming apparatus to reduce or prevent A-zone deletion.
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[0059] In some embodiments, the functional material can be present on the
surface of
an imaging member in an amount of between about 8 nanograms/cm2 and about 1000
nanograms/cm2; about 20 nanograms/cm2 and about 160 nanograms/cm2; or about 50
nanograms/cm2 and about 120 nanograms/cm2. The thin layer of functional
material on
the surface of an imaging member can have a thickness between about 1 nm and
about
60 nm, about 3 nm and about 20 nm, or about 8 nm and about 10 nm. In certain
embodiments, the functional material can be present on the surface of a
charging unit in
an amount of between about 8 nanograms/cm2 and about 1000 nanograms/cm2; or
about 20 nanograms/cm2 and about 160 nanograms/cm2; or about 50 nanograms/cm2
and about 120 nanograms/cm2. The functional material can be delivered to the
charging unit or imaging member at a rate of between about 0.1 mg/Kcycle and
about
20 mg/Kcycle; about 1 mg/Kcycle and about 10 mg/Kcycle ;or about 3 mg/Kcycle
and
about 8 mg/Kcycle.
[0060] Certain embodiments are drawn to methods of reducing printing defects
by an
image forming apparatus comprising: (a) providing a delivery member in the
image
forming apparatus, wherein the delivery member comprises a support member, and
a
first layer comprising a cross-linked elastomeric matrix, a stabilizing
polymer comprising
a polysiloxane backbone, and a functional material, disposed on the support
member,
and wherein the image forming apparatus further comprises an imaging member
having
a charge retentive surface, and a charging unit for applying an electrostatic
charge on
the imaging member; and (b) contacting the delivery member with a surface of
the
imaging member (e.g., surface of imaging member's overcoat) or a surface of
the
charging unit to apply a layer of the functional material to the surface of
the imaging
member or the surface of the charging unit. The delivery member, including the
cross-
linked elastomeric matrix, the stabilizing polymer comprising a polysiloxane
backbone,
and the functional material, can be as described above. The imaging member and
charging unit can be any known in the art. The imaging member can comprise a
protective overcoat in some embodiments.
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[0061] Embodiments disclosed herein can permit maximization of the amount of
functional material (e.g., paraffin oil) stored in a delivery member in order
to increase its
useful life and/or the life of an imaging member. To achieve this, it is
desirable that
passive diffusion of a functional material (such as, paraffin oil) during
parking/idling of
an image forming apparatus be eliminated or reduced, as in some embodiments.
Not to
be bound by theory, an incorporated stabilizing polymer can interact both with
the cross-
linked elastomeric matrix (e.g., PDMS matrix) and the functional material
(e.g., paraffin
oil) of a delivery member, which can mitigate incompatibility between the
functional
material and the cross-linked elastomeric matrix. In embodiments, the
inclusion of
stabilizing polymers in delivery members can control passive leaking of
functional
material (e.g., paraffin oil) from a delivery member, which can reduce or
prevent
wasteful consumption of the functional material and reduce or prevent
contamination of
components caused by delivery of excess functional material, thereby improving
the
quality of images formed.
[0062] The following Examples further define and describe embodiments herein.
Unless
otherwise indicated, all parts and percentages are by weight.
EXAMPLES
[0063] Example 1 ¨ Preparation of Formulations with Stabilizing Polymer
[0064] Three formulations of polydimethylsiloxane (PDMS) (Dow Chemical Co.)
and
paraffin oil, with and without a stabilizing polymer (Gelest) were prepared
and then
cured in polystyrene petri dishes. The three formulations were as follows: a)
PDMS:paraffin oil 2:1 (FIG. 4a); b) PDMS:paraffin oil:MHOMS
(methylhydrosiloxane-
octylmethyl siloxane) 2:1:0.5 (FIG. 4b); and c) PDMS:paraffin oil:pTDMS
(polytetradecylmethylsiloxane) 2:1:0.5 (FIG. 4c). The ratios were by weight.
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[0065] Paraffin oil started to diffuse from the PDMS in the PDMS:paraffin oil
2:1
formulation by weight (FIG. 4a) within 48 hours of curing. In contrast,
paraffin oil did not
diffuse from the PDMS in the formulations where stabilizing polymers (e.g.,
MHOMS
and pTDMS) were used (FIGS. 4b and 4c). FIG. 5 shows the three formulations
about
24 days after they were cured. The PDMS:paraffin oil 2:1 sample without the
stabilizing
polymer had paraffin oil droplets on its surface indicative of passive leaking
over time,
whereas the other two samples that contained stabilizing polymers (e.g., MHOMS
and
pTDMS) did not have paraffin oil droplets at the surface, indicating that
passive leaking
of paraffin oil was suppressed.
[0066] Example 2 ¨ Preparation of Delivery Rollers with Stabilizing Polymer
[0067] Three delivery rollers were prepared with formulations of PDMS,
paraffin oil, and
stabilizing polymer, as in Example 1. The three formulations by weight used in
making
the surface layers for the delivery rollers were as follows: a PDMS:paraffin
oil 2:1 (FIGS.
5a and 6a); bi) PDMS:paraffin oil:pTDMS 2:1:0.5 (FIGS. 5b and 6b); and c)
PDMS:paraffin oil:pTDMS 2:1:0.25 (FIGS. 5c and 6c). After curing, these
delivery rollers
were placed in contact with a BCR (bias charge roll) to evaluate the extent of
passive
diffusion onto the BCR after i) 24 hours (FIG. 5) and ii) after 5 days (FIG.
6).
[0068] After 24 hours, a significant amount of paraffin oil diffused from the
PDMS matrix
onto the BCR from the 2:1 PDMS:paraffin oil roller, whereas the rollers
containing
pTDMS as a stabilizing polymer did not diffuse paraffin oil. The amount of
paraffin oil on
the BCR from the 2:1 PDMS:paraffin oil roller was sufficient to cause image
defects and
exacerbate contamination on the BCR. After 5 days, a small amount of paraffin
oil
diffused onto the BCR from the delivery rollers with the stabilizing polymers,
but this
amount was not sufficient to cause detrimental image quality issues or
contamination.
For these delivery rollers to function properly, it was important that some
paraffin oil still
diffuse out of the roller onto the BCR.
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[0069] Example 3 ¨ Preparation of Prints Using Delivery Rollers
[0070] Delivery Rollers with surface layers containing a) PDMS:paraffin oil
(2:1), and b)
PDMS:paraffin oil:pTDMS (2:1:0.5) were integrated into Xerox DC250 CRU's
(customer
replaceable units) with overcoated photoreceptors. These surface layers
containing
paraffin oil only spanned two-thirds of the length of the imaging
member/photoreceptor,
so that there was a region to which paraffin oil was delivered to the charging
unit/imaging member (e.g., BCR/photoreceptor) and a control region (about one-
third of
the photoreceptor) to which no paraffin oil was delivered.
[0071] After 24 hours, the CRU's were inserted into a Xerox machine DC250 and
used
to print 100 prints.
[0072] FIG. 7a shows the first printed image (T=0) from the PDMS:paraffin oil
2:1 roller.
In the region with no paraffin oil, there was deletion of the fine bit lines,
whereas the
side with the paraffin oil had no such deletion. However, the side with the
paraffin oil
showed inefficient toner transfer (in the half-tone regions) due to the
presence of excess
paraffin oil where the roller was in contact with the BCR for 24 hours. FIG.
7b shows
T=0 (time zero) for the CRU with a PDMS:paraffin oil:pTDMS 2:1:0.5 delivery
roller;
deletion was evident on the side without paraffin oil and no deletion or
inefficient toner
transfer was apparent on the side with the paraffin oil, indicating that
paraffin oil was
delivered in an amount sufficient to prevent A-zone deletion.
[0073] Over 5 days, paraffin oil leaked from the PDMS:paraffin oil 2:1
delivery roller,
which exacerbated inefficient toner transfer when prints were made (FIG. 8a).
The CRU
with the PDMS:paraffin oil:pTDMS 2:1:0.5 delivery roller did not deliver
excessive
amounts of paraffin oil after 24 hours or after 5 days. FIG. 8b shows the T=0
(at time
zero) IQAF (image quality analysis facility) image obtained from this roller
after sitting in
the CRU for 5 days before printing. There was no deletion on the side of the
image with
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the delivery roller (e.g., with paraffin oil), whereas there was deletion on
the side
without. There was successful toner transfer because there was not an
excessive
amount of paraffin oil delivered as the roller did not passively leak paraffin
oil over the 5
days it was sitting idle in the CRU.
[0074] Leaking of paraffin oil over time causes toner contamination of the BCR
and the
delivery roller. This type of contamination can lead to streaking in prints
due to
inefficient charging of the imaging member (e.g., photoreceptor) by the
contaminated
BCR. FIG. 9a shows toner contamination on the PDMS:paraffin oil 2:1 delivery
roller
after running 100 prints after the roller had been left idle in the CRU for 5
days; FIG. 9b
shows no toner contamination on the PDMS:paraffin oil:pTDMS 2:1:0.5 delivery
roller
after running 100 prints using the roller that had been aged 5 days in the
CRU. The lack
of contamination indicated that excessive amounts of paraffin oil had not
leaked from
the roller in that idle time. FIG. 10a shows the T = 100 print obtained from
the CRU with
the PDMS:paraffin oil 2:1 delivery roller. Streaks in the prints were caused
by the
contamination.
[0075] The Examples demonstrated that a stabilizing polymer (pTDMS or MHOMS)
helped stabilize paraffin oil in a PDMS matrix, and the passive leaking of
paraffin oil
from the PDMS matrix delivery rollers was prevented or reduced. Delivery
rollers
containing the stabilizing polymers delivered sufficient paraffin oil to
lubricate and
prevent A-Zone deletion. There was less contamination on the BCR when a roller
containing stabilizing polymer was used as compared to a roller without
stabilizing
polymer.
[0076] To the extent that the terms "containing," "including," "includes,"
"having," "has,"
"with," or variants thereof are used in either the detailed description and
the claims,
such terms are intended to be inclusive in a manner similar to the term
"comprising."
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[0077] Further, in the discussion and claims herein, the term "about"
indicates that
the values listed may be somewhat altered, as long as the alteration does not
result
in nonconformance of the process or structure to the illustrated embodiment.
[0078] Notwithstanding that the numerical ranges and parameters setting forth
the
broad scope of the present teachings are approximations, the numerical values
set
forth in the specific examples are reported as precisely as possible. Any
numerical
value, however, inherently contains certain errors necessarily resulting from
the
standard deviation found in their respective testing measurements. Moreover,
all
ranges disclosed herein are to be understood to encompass any and all sub-
ranges
subsumed therein. For example, a range of "less than 10" can include any and
all
sub-ranges between (and including) the minimum value of zero and the maximum
value of 10, that is, any and all sub-ranges having a minimum value of equal
to or
greater than zero and a maximum value of equal to or less than 10, e.g., 1 to
5. In
certain cases, the numerical values as stated for the parameter can take on
negative
values. In this case, the example value of range stated as "less than 10" can
assume values as defined earlier plus negative values, e.g., -1, -1.2, -1.89, -
2, -2.5, -
3, -10, -20, and -30, etc.
[0079] It will be appreciated that variants of the above-disclosed and other
features
and functions, or alternatives thereof, may be combined into many other
different
systems or applications. The claims should not be limited by the preferred
embodiments described herein but should be given the broadest interpretation
consistent with the specification as a whole.
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